The present invention relates generally to a flow control device for a fluid cylinder and, more particularly, to a flow control device for a fluid cylinder for a work piece holder or gripper assembly.
It is known to implement a pneumatic cylinder with a workpiece holder or gripper or the like, such that extension and retraction of a piston rod of the cylinder causes opening and closing of the workpiece holder or gripper assembly. Typically, the air cylinder has no cushioning affect in either direction, which may result in excessive wear and even premature failure of the cylinder or workpiece holder. In order to reduce the shock of the rapid movement of the cylinder in either direction, cushioning devices, such as elastic cushions or the like, have been proposed. However, such cushioning devices may not achieve desired operational results and may require changes within an existing cylinder to facilitate installation of the cushioning device. Additionally, the elastic cushioning devices do not assist in control of the extension and retraction of the piston rod, such that the speed of the opening or retracting stroke is the same in both directions.
The present invention is intended to provide a fluid flow control device or apparatus for controlling and restricting fluid flow to and from a fluid cylinder in order to control the fluid flow in either direction and to further control the rate of extension or retraction of the piston within the cylinder. The flow control device allows greater flow of fluid in one direction, such as in a direction to extend the piston from the cylinder, while restricting fluid flow in the other direction, in order to reduce the retraction speed of the cylinder and cushion the movement of the piston within the cylinder. The flow control device is mountable to a backing plate of the pneumatic cylinder and is integral within the backing plate to substantially obviate the need for modification of the cylinder and its internal components.
According to a first aspect of the present invention, a flow control apparatus is adaptable to be implemented at a fluid cylinder having a backing plate and being extendable and retractable in response to fluid flow through the backing plate. The flow control apparatus includes a flow restricting member adapted for positioning at the backing plate and a flexible sealing member. The flow restricting member includes a first passageway and a continuous sealing surface. The flexible sealing member is positioned around the sealing surface and adapted for sealing engagement with the backing plate. The flexible sealing member is movable to engage and disengage the sealing surface and disengages the sealing surface to at least occasionally define a second passageway through the flow control apparatus. The sealing member is movable to disengage the sealing surface in response to fluid flow in a first direction such that fluid flows through the second passageway in the first direction. The sealing member is movable to engage the sealing surface in response to fluid flow in a second direction to limit fluid flow between the sealing member and the sealing surface in the second direction. Fluid flows in the second direction through the first passageway. The first direction is generally opposite to the second direction and the flow control apparatus restricts fluid flow in the second direction to control operation of the pneumatic cylinder.
Preferably, the flow restricting member and the sealing member are positionable within a recess in the backing plate. Preferably, the pneumatic cylinder is applicable to a workpiece holder, such that fluid flow in the first direction causes extension of a piston within the cylinder to close the workpiece holder, while fluid flow in the second direction causes retraction of the piston to open the workpiece holder.
In one form, the flow restricting member includes a base portion and a generally cylindrical portion extending therefrom and defining the sealing surface. The base portion defines a third passageway extending at least partially thereacross, wherein the third passageway provides fluid flow to the first and second passageways. The sealing member is secured within a recess in the backing plate and retains the flow restricting member between an inner end wall of the recess and the sealing member. Preferably, the sealing member includes a generally rigid body portion adapted to engage the side wall of the recess and a flexible sealing portion extending from the body portion and being adapted to engage the sealing surface of the flow restricting member in response to fluid flow in the second direction. Preferably, the base portion is seated against the end wall of the recess and includes a chamfered perimeter edge to allow fluid flow around the base portion between at least one end of the third passageway and a supply or exhaust port in the recess of the backing plate.
According to another aspect of the present invention, a pneumatic cylinder for extending and retracting a piston in response to fluid flow is adaptable for connection to a workpiece holder. The pneumatic cylinder comprises a cylinder housing for housing the piston, a backing plate at one end of the housing, and a flow control apparatus. The piston is extendable and retractable along and within the housing in response to fluid flow. The backing plate has at least one port for fluid flow therethrough and a recess having an inner end wall portion interconnected with the port and a side wall portion extending from the end wall portion toward the cylinder housing. The flow control apparatus is positionable within the recess and includes a flow restricting member and a flexible sealing member. The flow restricting member is positionable at the inner end wall portion of the recess and defines a first passageway and a generally uninterrupted, continuous sealing surface. The flexible sealing member includes a body portion and the sealing portion. The body portion is engaged with the side wall of the recess and the sealing portion is positioned around the sealing surface of the flow restricting member for sealing engagement with the sealing surface. The sealing portion is movable from the sealing surface to at least occasionally define a second passageway therebetween. The sealing member is movable to disengage from the sealing surface of the flow restricting member in response to fluid flow in the first direction such that fluid flows through the first and second passageways in the first direction. The sealing member is movable to engage the sealing surface in response to fluid flow in the second direction to limit fluid flow through the second passageway in the second direction, while allowing fluid flow through the first passageway. The flow control apparatus thereby restricts fluid flow in the second direction to control operation of the pneumatic cylinder.
Therefore, the present invention provides a flow control apparatus for a cylinder. The flow restricting member and the sealing member are cooperatively operable to allow fluid flow in a first direction from the port in the backing plate through both the first and second passageways. The flow restricting member and the sealing member are further cooperatively operable to allow fluid flow in the second direction through the first passageway to the port, while substantially precluding flow through the second passageway. The flow control apparatus thus provides for controlled movement of the piston within the cylinder via fluid flow in the second direction.
These and other objects, advantages, purposes and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.